Conventional cellular window shades are well known in the art. These shades, which are typically referred to as honeycomb shades or panels, include shading cells made of flexible materials that are suspended from a head rail and connected to the head rail by one or more control members, such as cords. As with many types of window coverings, the head rail is secured to a window frame or other architectural substrate to fix the window covering in the desired opening. Cellular window shades are opened and closed by collapsing or expanding the cellular panels, such as by raising or lowering the control member.
A cellular panel may be suspended from the head rail by securing a portion of the uppermost cell of the array with the head rail itself. For example, a rigid strip of material can be inserted into the uppermost shading cell of the cellular panel so that this uppermost shading cell with the rigid strip can be positioned with the head rail. To support the strip, the head rail may define a pair of braces that support the rigid strip and the uppermost cell such that the rest of the cellular structure is suspended therefrom.
In addition to supporting the shading cells, it is desirable that the position of the shading cells relative to the head rail be maintained. More particularly, it is desired that the uppermost shading cell and the head rail not be movable relative to one another due to the potential for misalignment of the cells, and undue wear to the cellular material caused by rubbing with the head rail. Different fastening techniques have been utilized to operatively secure the shading cells to the head rail. For example, the rigid strip may be inserted along with the uppermost shading cell and a side cover inserted into the head rail to prevent lateral movement of the rigid strip and uppermost shading cell. This side cover limits the lateral movement and prevents the strip or the cellular panel from sliding out of the head rail, such as during installation. Unfortunately, the described method is ineffective to prevent smaller shifts or movements of the rigid strip or uppermost shading cell while in the head rail. For example, the forces exerted by the user when opening or closing the window covering can cause minor shifts in position of the material relative to the head rail or control members, which are typically guided through holes in the panel. Over time, this movement can result in damage to the cellular panel.
Another method for securing the rigid strip and uppermost cell in the head rail employs an adhesive to attach the rigid strip to the uppermost shading cell. The combination of the strip and cell are then held via an interference fit within the head rail. The adhesive may also be used to secure the shading cell to the side cover or cap of the head rail. The uppermost shading cell with its rigid strip is then inserted into the head rail until the side cover covers and caps an open end of the head rail. While this method prevents the relative movement of the strip, the method is cumbersome and inefficient because the glue is typically applied uniformly on the surface of the strip to adhere to the interior of the uppermost shading cell, and the insertion of the rigid strip into the cell may rip the flexible material as it is inserted. The adhesive also makes the insertion of the strip into the cell difficult. Also, since the uppermost shading cell and the rigid strip are secured to one another before insertion into the head rail, the flexible material of the uppermost cell may be damaged during assembly. Further, the rigid strip, cellular panel, and end cap are permanently affixed to one another, thereby limiting the ability to repair, clean, or replace the cellular panel.
Accordingly, there is a need for a window covering with an improved fastening device for securely assembly shading cells with a head rail that allows greater flexibility.